The invention is directed to means for filling a tube or similar workpiece with fluid and for pressurizing the fluid within the workpiece.
Various manufacturing and industrial processes require that tubes or vessels be filled with liquid and then pressurized. Examples of such processes include: expanding tubes within a forming die cavity as described in U.S. Pat. Nos. 4,567 743 and 4,829,803 to Cudini; expanding a tubular liner to form a composite lined pipe as described in U.S. Pat. No. 3,359,624 to Cours et al; and pressure testing of fabricated pressure vessels. In general, such processes include the following steps: sealing of the openings of the tube or vessels workpiece; filling of the workpiece with fluid; pressurizing the fluid within the workpiece to achieve the particular desired result such as forming, expanding or pressure testing; depressurizing the fluid; draining the fluid; and removing the sealing means to release the workpiece.
Conventional devices to carry out the above processes generally utilize a single sealing means which operates to prevent fluid leakage during the low pressure filling and draining stages, as well as during the high pressure pressurized stages. Examples of such devices are described in U.S. Pat. Nos. 4,788,843 to Seaman et al. and 3,625 040 to Gain When such devices are used in a repetitive high volume manufacturing environment, such as automobile parts manufacturing for example, the sealing means are generally the first part of the device to fail, and are therefore the cause of significant delay and machine downtime. Such sealing means relies upon the contact between the workpiece and a flexible gasket to maintain a fluid seal. Workpieces often have burrs on the edges of their openings which damage the gasket, and in any case through repeated use the flexible gasket eventually fails necessitating replacement. Conventional devices often do not include means to accurately predetermine or limit the degree of flexible gasket compression. A gasket which is compressed to an inadequate degree will leak, whereas an over compressed gasket will fail prematurely due to material fatigue or over stressing. Frequent replacement of such gaskets results in costs associated with maintenance and inefficiency during machine downtime.
The failure of such conventional sealing means also subjects the machine operators and adjacent machinery to the risk of harm from the leakage of high pressure fluid. Some form of machine guard or personal protective equipment may often be required by various local safety regulations in association with conventional devices as a result.
In such conventional devices fluid often enters the workpiece via a single input-output circuit of piping. In order to quickly fill and drain the workpiece with fluid a relatively large diameter, piping circuit is desirable, whereas to pressurize the fluid only a relatively small diameter piping circuit is required due to the low quantity of flow and a small diameter is desirable due to the increased wall thickness required if large diameter pipes are used for high pressure fluid circuits. In U.S. Pat. No. 3,359,624 to Cours et al. a device is described which includes a high flow-low pressure circuit for filling and draining, as well as low flow-high pressure circuit for pressurizing the liquid. Such conventional devices reduce the amount of time required to fill and drain the workpiece but suffer from the disadvantage that costly valving and valve controls are required to separate the two circuits. In addition, the valving adds a further process time to operate, and introduces additional maintenance costs.